With the development and popularization of membrane separation technology, requirements to the high performance of membrane are ever-increasing. Because of the excellent thermal stability, chemical stability, acid and alkali resistance, erosion-resistant of microbe and oxidation resistance, some polymers have become one of the important components in the membrane materials. However, the membrane fouling is still a major problem in the development of membrane separation technology. Especially the membrane fouling that is caused by the adhesion and growth of bacteria on the surface of the membrane during the filtration, resulting in the reduction of membrane separation performance and sharp decrease of the membrane flux, which limits the application of membrane in many aspects. In the field of membrane preparation, therefore, it is crucial to prepare new membrane materials, modify the physical and chemical properties of membrane materials, enhance the antibacterial properties and antifouling capacity of membrane.
At present, there are a lot of reports about the antibacterial and antifouling modification for polymeric separation membrane. For example, CN104524986A describes processes to prepare the hydrophilic antimicrobial membrane: immersing the basal membrane in the aqueous solution of dopamine to form a polydopamine layer on the membrane surface via self-assembly of dopamine, and reacting with the aqueous solution of polyethyleneimine to get the hydrophilic antimicrobial membrane via cationization. In CN104190274A, the silver nano-particle/Zwitterion polymer brush grafted polyvinylidene fluoride membrane were prepared by using polyvinylidene fluoride (PVDF), Silver ion, and zwitterion monomer as the raw materials, which has antibacterial activity. But the modification mentioned above, usually attained by surface deposition, grafting, layer-by-layer self-assembly or cross-linking to combine the inorganic small molecule or organic macromolecule antibacterial agent with the functional membrane material. These modification methods are complex and not conducive to commercial production. In addition, the modified layer is easy to take off, which leads to the loss of antifouling capacity. The antibacterial effect of the modified membrane has not been tested by long-term experiment. Therefore, it needs to be further verified whether the modified membrane has a long-term antibacterial and antifouling capability.
As a kind of well-known bactericide, quaternary ammonium salt is widely used in water treatment and petroleum mining industry. The mechanism of this bactericide is sterilization by contact. In details, bactericide as cationic monomer adsorbs the negatively charged bacteria and gathers in the cell wall by electrostatic force, hydrogen bond and interaction of surfactant and protein molecules, which forms the steric effect, leads to inhibition of bacterial growth and death.
Therefore, this kind of bactericide display high efficiency, low toxicity, resistance to variety of pH, chemical stability and easy to use. With such benefits, the bactericide is suitable for resisting adhesion of microorganisms on the membrane surface, thereby preventing fouling of the membrane surface by microorganism and its secretion.